Presentation and management of benign mediastinal teratomas.

Mediastinal teratomas are uncommon, making up only about five to ten percent of all mediastinal tumors and are thought to occur in approximately 1 in 3400 hospital admissions. There are many names for this tumor, but the term "benign teratoma" is fitting. The word "teratoma" is derived from the Greek word "teras", meaning monsters. They have been defined as "tumors that are composed of tissue that is foreign to the organ or anatomic site in which they arise" Alternatively, mediastinal teratomas may arise from cells adjacent to the third or fourth brachial cleft. Whatever the cell of origin, these tumors have potential to express all three of the germ cell layers, ectoderm, mesoderm and neuroderm.